So I have this old backpack that's gone mouldy but its still pretty sturdy, so I'm planning to dunk it in vinegar and then fill it with sand/gravel/rocks/hobo corpses and start lifting/tossing it around. Question is, if I want to do squats with it, can I wear it like a backpack, or should I hoist it up onto one shoulder like in Rabbit's video?

That's a single rep standard. 85-90% of that x3-5 is good too. If you're at all serious, I would strongly suggest picking up Rippetoe's Starting Strength and work from there. His technique is great.

That absolute minimum I would say is your bodyweight x5, but that's pretty bad.

If you've never lifted seriously before, you can gain a lot of strength pretty quickly. If you squat correctly (note: correctly), it's actually good for your knees.

I find it hard to lift heavy with the legs and or back because if my leg muscles are too sore i can't practice boxing properly, and i prefer "saving" myself for that so not to get my ass kicked. I guess what im asking is the frequency you would work squats, and with what would you combine it to make a whole session out of it. thenx

If you really have no equipment and dont want to just do bodyweight squats, think about progressing to pistol (one legged) squats, and when that gets easy -> jumping pistol squats. They're really not the same as having a loaded barbell on your back, but you gotta do what you gotta do to be awesome.

I find it hard to lift heavy with the legs and or back because if my leg muscles are too sore i can't practice boxing properly, and i prefer "saving" myself for that so not to get my ass kicked. I guess what im asking is the frequency you would work squats, and with what would you combine it to make a whole session out of it. thenx

Don't be a *****? I'm 38. I squat 2-3x/week and play Judo 2-4 days a week.

If you ramp up slowly you won't be sore. Soreness is (mostly) from the negative portion of the exercise.

I've seen many gym rats fail at holding gum gwai sic for more than a few seconds. I can hold that position for 5 minutes. Take a guess as to why.

First off, a point of order: this is squat month, not deadlift month. Look at the joint angles in that picture, then compare them to the starting position of a deadlift vs. the bottom of a back squat.

Second, you can hold that position for five minutes because you've been practicing that particular position and evidently have a very high tolerance for boredom. It remains that getting better at that particular position is not going to get you any stronger, and 110lbs of load, even active load, is only something worth mentioning if you're throwing it for distance or lifting it with one hand.